Granular detergents have so far been principally prepared by spray drying. In the spray drying process the detergent components, such as surfactants and builders, are mixed with as much as 35-50% water to form a slurry. The slurry obtained is heated and spray dried, which is expensive. A good agglomeration process, however, could be less expensive.
There are many prior art nonspray-drying processes which produce detergent granules. Most require neutralisation of the anionic surfactant acid, immediately before, or in the course of, a granulation step.
However, these processes have certain limitations. The close coupling of the neutralization and granulation steps considerably limits the range of processing conditions that can be used. Furthermore, if the anionic surfactant chosen is not stable in the acid form (e.g. alkyl sulphate) it is necessary to have close coupling of the sulph(on)ation with the neutralization and granulation stages. This results in considerable limitations in the logistics and/or design of the facilities for these processes as well as an important increase in complexity and difficulty of control systems for the overall process.
The purpose of this invention is to provide a high active anionic surfactant paste which has rheological properties that make it suitable for pumping, storing, transportation between manufacturing sites, and further processing by agglomeration into high active detergent particles. It is an important feature of the invention that the granulation/agglomeration step is completely uncoupled from the sulph(on)ation step.
It has now been found that the addition of small amounts of alkyl ethoxy sulphate greatly improves the rheological characteristics of the surfactant paste.
GB2021141, published Nov. 28, 1979, discloses surfactant paste compositions within a narrow concentration range in the fluid lamellar (`G`) phase.
GB2116200, published Sept. 21, 1983, discloses paste compositions of up to about 40% by weight of anionic surfactant containing ethoxylated surfactants as dissolution aids, and forming agglomerates from these compositions.
EP 403148, published Dec. 19, 1990, describes high active surfactant compositions containing less than 14% water. The use of process aids to reduce viscosity of the high active paste in a neutralisation loop is described. Polyethylene glycol and ethoxylated nonionic surfactants are disclosed as suitable process aids.
EP 399581, published Nov. 28, 1990, describes high active surfactant compositions containing ethoxylated anionic surfactants and ethoxylated nonionic surfactants.